You can think of Mailhero as a super-human shield between you and the mails sent by evil spammers.
It's really quite simple. Mailhero receives all mail coming to all addresses @mailhero.io. If the mail alias used (the first part of the address, ie. firstname.lastname@example.org) is active, then we forward it to your real address. If the alias has been inactivated by you, then we don't and the mail instead ends up in the great big bit-bucket in the sky.
I have been creating webapps like this for a long time and I always make sure to have really low infrastructure costs for any project. This ensures that I can keep sites running indefinitely. The most widespread site that I have been a part of launching is probably Shorl.com which has been up and running since 2001 even though it has had millions of users over the years (longer than, say, Gmail which was first launched as a closed beta in 2004).
That is a sound question. Firstly, you should not trust any email service provider 100%. I would urge you to use PGP or similar software for sensitive data, and to only use a self-hosted mail server for important accounts. But, the purpose of Mailhero is rather the opposite: to ensure that unwanted mail does not reach you. Therefore, my suggestion is that you try out Mailhero for those cases were you aren't sure of the other parties intention. That way you will get a feeling for how the service works, how well it performs and, hopefully, how trustworthy it really is.
It was created by Josef Falk who has been creating sometimes useful and sometimes weird projects on the Internet as a hobby for a couple of decades now. He is one of the authors of Shorl.com mentioned above, Vinranka.com (A Swedish site which ranks wines based on the words in their descriptions), Scropple.com (a tool that let's you find the perfect word in Scrabble, Wordfeud, Betapet etc.), Upperct.com (a dynamic youtube video ranker) and others too small or silly to mention.
You can reach Joe at email@example.com, if you happen to have any questions what so ever.
By accessing the web site at mailhero.io, you are agreeing to be bound by these web site Terms and Conditions of Use, all applicable laws and regulations, and agree that you are responsible for compliance with any applicable local laws. If you do not agree with any of these terms, you are prohibited from using or accessing this site. The materials contained in this web site are protected by applicable copyright and trademark law.
In no event shall Mailhero or its suppliers be liable for any damages (including, without limitation, damages for loss of data or profit, or due to business interruption,) arising out of the use or inability to use the materials on Mailhero's Internet site, even if Mailhero or a Mailhero authorized representative has been notified orally or in writing of the possibility of such damage. Because some jurisdictions do not allow limitations on implied warranties, or limitations of liability for consequential or incidental damages, these limitations may not apply to you.
The materials appearing on Mailhero's web site could include technical, typographical, or photographic errors. Mailhero does not warrant that any of the materials on its web site are accurate, complete, or current. Mailhero may make changes to the materials contained on its web site at any time without notice. Mailhero does not, however, make any commitment to update the materials.
Mailhero has not reviewed all of the sites linked to its Internet web site and is not responsible for the contents of any such linked site. The inclusion of any link does not imply endorsement by Mailhero of the site. Use of any such linked web site is at the user's own risk.
Any claim relating to Mailhero's web site shall be governed by the laws of Sweden without regard to its conflict of law provisions.
General Terms and Conditions applicable to Use of a Web Site.